High-frequency signaling system



Dec. 10, 1929.

BIRD 1,739,384

HiGH FREQUENCY SIGNALING SYSTEM Filed Jan. 14, 1927 Inventor: Lesteh I". Bird,

H is Attohngy Patented Dec. 10, 1929 UNITED STATES PATENT OFFICE I LESTER F. BIRD, F SCHENECTADY, NEw YORK, ASSIGNOR :20 GENERAL ELEc EIe COMPANY, A CORPORATION or NEW YORK HIGH-FREQUENCY SIGNALING SYSTEM Application filed January 14, 1927. Serial No. 161,191.

My invention relates to high frequency signaling systemsof the type in which both a transmitting circuit and a receiving circuit are employed. More particularly my invention relates to systems of the type described in copending applications, of Emmett F. Carter, Serial No. 161,188 filed January 14, 1927, and Patent No. 1,696,593 issued December 25, 1928, both of which are entitled High-frequency signaling systems and which are assigned to the same assignee as the present application.

. In the above mentioned application means are described for controlling the volume level of the received signal at the head phones by placing a normally inactive shunt across one of a plurality of tuned circuits in the receiving circuit of the signaling system and rendering saidshunt active responsively to the intensity of the received high frequency impulses. In the above patent a similar shunt is rendered active responsively to the functioning ofthe transmitting circuit to provide a device for protecting the receiving circuit from energy which may enter it from the transmitting circuit.

One of the objectsof my invention is to provide such a device which will operate responsively to both the intensity of the received high frequency impulses and to the functioning of the transmitting circuit, or to either of these. Another purpose of my invention is to provide a system of this type in which the signals which are impressed upon the antenna or wire line system willbe faithfully reproduced at the receiver. A further purpose of my invention is to provide a signaling system having the characteristics mentioned above and in which simultaneous transmission and reception may take place.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation will best be u'nderstod by reference to the following description taken in.connection with the accompanying drawing, in which I have illustrated, diagrammatically, one form of my invention.

Referring to the drawing, 1 indicates the usual antenna or wire line circuit whlch comprises a part of the signaling system; 2 indicates generally the receiving circuit; 3 indicates generally the transmitting circult and 4 indicates the wire line leading to the oper- 4 10 represents the usual balancing network for.

these transformers.

In the receiving c1r'cu1t, 11 indicates an electran discharge devicewhich is employed as a detector. It will, of course, be understood that any type of detector might be used. This device has an input circuit which comprises the grid 12, condenser 13,'the secondary Winding of the input transformer 14, conductor 15, conductor 16, resistance 17, conductor 18 and cathode 19. The output cireuitof this detector comprises the anode 20, the primary winding of the output transformer 21, a source of potential 22, conductor 23, conductor 16, resistance 17, conductor. 18, and the cathode 19. For the purpose of tuning the input circuit to the detector a condenser 24 is provided across the secondary winding of the input transformer 14. 25 indicates an electron discharge device having'an anode 26 which is connected to one side of the input circuit and grid 27 which is associated with the resistance 17 through a conductor 28, a' portion of the source of potential 29 and con--' ductor 18. The cathode 30 of the electron discharge device 25 is associated with the opposite side of the resistance 17 through the conductors 15' and 16, and this point on the re- 1 sistance 17 is preferably connected to ground potential through conductors 16 and 31. A source of potential 29 is connected between the cathode 19 through a suitable choke coil to the grid 12 of the detector 11. This source of potential serves to sup-ply a negative bias to the grids 12 and 27 of the detector 11 and the electron discharge device 25 with respect to their respective cathodes. The primary winding of the transformer 14 is connected to the coupling transformer 6 through conductors 32, which comprise a circuit in which there is no tuning.

With reference to the transmitting circuit, only so much of this circuit is shown as is necessary to an understanding of my invention. 40 represents the high frequency oscillation generator of the transmitting circuit, the operation of which is controlled by a control electron discharge device 35. The rectangle 33 represents the usual apparatus associated with the audio channel of the transmitting circuit, this apparatus being associated with the coupling transformer 9 through the input circuit 8 and with the grid 34 of a control electron discharge device 35, by means of the conductor 36. The anode 37 of the control electron discharge device 35 is connected through a conductor 38 to the cathode 39 of the oscillation generator 40.

i Anode 41 and grid 42 of the oscillation gener-- ator 40 are connected through conductors 43 to the usual oscillatory circuit and radio frequency amplifying apparatus, which is represented by the rectangle 44, the output of this apparatus being connected to the coupling transformer 6 through the output circuit 5. The anode 4'1 is supplied with a suit: able high potential from the direct current source 53 through choke coil 54. The cathode 45 of the control electron discharge de- 85vice is connected through a conductor 46 direct current potential of the anode 37 from the cathode 45 of the electron discharge device 35. The condenser 51 is provided between the conductor 47 and the conductor 31 for the purpose of bypassing alternating currents flowing in the conductor 47 and the choke coil 48 is provided in the conductor 47 for the purpose of preventing these alter natingcurrents from flowing into the receiv ing circuit. Condensers52 are provided f r the purpose of bypassing alternating currents flowing in the conductors 16 and 18 out of the resistance 17 The operation of my circuit is as follows: During normal reception current will be flowing in the output circuit of the detector 11 through the anode 20, space between the anode 20 and cathode 19 of the detector 11, conductor 18, resistance 17, conductor 16, conductor 23, source of potential 22, primary winding of the output transformer 21, bac

to the anode 20. Hence a potential will. exist on the resistance 17 having the polarity indicated in the drawing. The sum of this potential and that portion of the source of potential 29 which is between the conductor 28 and the conductor 18 is sufficient to place a negative bias upon the grid 27 of the electron discharge device 25 sufiicient to prevent the passage of any current from the anode 26 to the cathode 30. Hence, this electron discharge device will be inactive.

Assuming now that the received high frequency carrier wave so varies as to produce a signal at the head phones which is of greater volume than is desired. The direct current flowing in the output circuit of the detector 11 will then increase causing a corresponding increase'in the potentialon the resistance 17. This increase of potential will cause the potential on the grid 27 to become decreasingly negative or even positive with respect to the cathode 30 and a current will Likewise assume that during normal operation ofthe receiving circuit, the operator 1" speaks into the microphone at the operators -f'.

station. Energy will then' be transferred through the input circuit 8 and audio frequency apparatus 33 and audio frequency voltages will be impressed upon the grid 34 I through the conductor 36. This will lower the impedance between anode 37 and cathode 45 and cause a potential to exist between anode 41 and cathode 39 of the oscillation generator 40. High frequency oscillations. will then be produced in the oscillatory circuit which is excited through the conductors '43 from the oscillation generator 40. These will-be amplified in the amplifying apparatus 44 and transmitted to the antenna or wire line'circuit 1 through the output circuit 5 and coupling transformer 6. Some portion of this energy and particularly energy derived from currents of the side band frequencies will be impressed upon the input circuit of the detector 11 throughthe conductors 32 and input transformer 14. Upon the initiation of these high frequency currents. by the oscillation generator 40 a direct current will flow from the positive side of the source of potential 53 through the choke coil 54, anode 41, space between the anode 41 and cathode 39, cathode 39, conductor 38, anode 37, space between the anode 37 and cathode 45,-oathode 45, conductor 46, conductor 47, choke coil 48, a por tion of resistance 17, conductor 16 and conductor 31 to t e negative side of the source of potential 53. This likewise produces a source of potential uponv the resistance 17 having the polarity indicated in the draw ing which in turn causes the grid 27 of the electron discharge device 25 to assume a decreasingly negative or positive potential with respect to the cathode 30. Thus, the electron discharge device 25 will become a comparatively low resistance shunt across the tuned input circuit of the detector, thereby causing this circuit to be detuned and the transmission of energy through the circuit to be diminished.

It may thus be seen that the resistance 17 constitutes a source of potential variable responsively to the functioning of the transmitting ,Tcircuit and to the intensity of the high frequency impulses which are impressed upon the detector, or to either of these, for varyingQthe potential on the grid 27 of the electron-discharge device 25.

By utilizing a hybrid coil as 'a coupling transformer 6 and by properly adjusting the network' 10 currents of the frequency 0 the transmitted carrier will be substantially balanced out in this transformer and only energy derivedl-from currents of the side band frequencies will be transmitted into the input circuit of the detector through the circuit 32. This being the case, only a small amount of protection from the transmitting circuit, by means of the electron discharge device 25, will-(be required. Hence by properly adjustingthe circuits as by varying the position of the point 49 upon the resistance 17 or the position of the tap upon the source of potential 29, I am enabled so to adjust the bias upon the grid of the electrondischarge device 27 as to cause this device to provide the necessary protection against these side band frequencies and at the same time not greatly to impair the reception of signals received over the antenna or wire line 1. Hence with such an arrangement both the transmitting circuitand the receiving circuit may function simultaneously without interference in the receiving circuit from thetran smitting c1rcu1t.'

,It may thus be seen that I have provided a combination protective and volume control device 111 which a slngle electron discharge? device may be employed for both purposes. I have likewise provided a device adapted for carrier current and radio trans mission and reception, having the characteristics nientioned above and the additional feature that transmission and reception may be made without departing-from the scope thereof, as set forth in the appended claims.

.What I 'claimas new and desire to secure by Letters Patent of the United States, is:

1. In a signaling system comprising a transmitting circuit and a receiving circuit,

an electron discharge device having a cathode and an anode, said cathode being'connected to one side ofsaid receiving'circuit and said anode being connected to the other side of said receiving circuit, and a.source of potential which is variable responsively to the n intensity of the received high frequency impulses and to the functioning of said transmitting circuit for controlling the impedance "between said cathode and said anode.

In a signaling {system comprising a transmitting circuit and a receiving circuit, an electron discharge device having an anode,

a cathode and a grid,'said anode being cons5 nected to one side of said receiving circuit' and said cathode beingconnected to the other side of said receiving circuit, and a source of potential which is variable responsively to the intensity of the received high frequencyimpulscs-and to the functioning of said transmitting circuit for controlling the potential on said grid.

In a signaling system employing a transmitting circuit and a receiving circuit, a control device comprising an electron discharge device having an anode, a cathode and a grid, said anode being connected to one side of said receiving circuit and said cathode being connected to the other side of said receiving circuit, a detector in said receiving circuit having an output circuit, a vacuum tube oscillation generator in. said transmitother side of said tuned circuit, and a source of potential which is variable responsively to the intensity of the. received high. frequency'impulses and to the functioning of said transmitting circuit for varying the impedance between said cathode and said anode. 7

5. The combination in a signaling system comprising a transmitting circuit and a receiving circuit, of a control device comprising a tuned circuit in -said receiving circu'it. an electron discharge device havin an anode, a cathode and a grid, said anode being connected to one side of said tuned circuit and 30 generator.

said cathode being connected to the other side of said tuned circuit, and a source of potential which is variable responsively to the intensity of the received high frequency 5 impulses and to the functioning of said transmitting circuit for varying the potential on said grid.

6. In a signaling system comprising a transmitting circuit and a receiving circuit, a control'device comprising a tuned circuit in said receiving circuit, a normally inactive shunt for said tuned circuit, andmeans variable responsively to the intensity of the received high frequency impulses and to the functioning of said transmitting circuit for rendering said shunt active and detuning said tuned circuit.

7 In a signaling system employing a transmitting circuit and a receiving circuit,

520 a control device comprising a tuned circuit in said receiving circuit, a normally inactive shunt for said tuned circuit, a detector in said receiving circuit having an output circuit, a vacuum tube oscillation generator in said transmitting circuit having an anode circuit and means for varying the impedance of said normall inactive shunt, said means being include in the output circuit of said detector and in the anode circuit of said oscillation V 8. In a signaling system employing a transmitting circuit and a receiving circuit, a control device comprising a tuned circuit in said receiving circuit, an electron discharge device having an anode, a cathode and a grid,

said anode being connected to one side of said tuned circuit and said cathode being connected to the other side of said tuned circuit, a detector. in said receiving circuit having an output circuit, a vacuum tube oscillation generator in said transmitting circuit having an anode circuit, a resistance included in said output circuit and in saidanode circuit the potential on said grid being variable respon- 5 sively to the potential on said resistance.

9. In a signaling system employing a transmitting circuit and a receiving circuit, a

control device comprising a normally inactive shunt for said receiving circuit, and means responsive to the intensity of the received high frequency impulses and to the.

functioning of said transmitting circuit for rendering said shunt active.

10. The combination in a signal system of a transmitting circuit, a rec'eiving circuit, an

impedance connected in shunt with said receiving circuit, means for rendering said impedance variable in response to the intensity of the received signalimpulses and means for controlling said impedance in response to operation of the transmitting circuit.

11. The combination in a signal system, of a transmitting circuit, a receiving circuit, a tuned circuit in said receiving circuit and means for controlling the tuning of said atransmitting circuit, a receiving circuit, an electron discharge device having an anode, a

'13. The combination in a signal system, of

cathode and a grid, said anode and cathode being connected in shunt circuit relation to said receiving circuit and means responsive to the intensity of the received signal impulses and to operation of the transmitting circiuit for controlling the potential on said grl y 14.. The combination in a signal system, of a transmitting circuit, a receiving circuit, an electron discharge device connected in shunt with said receiving circuit and means responsive to the intensity of signal impulses on'said receiving circuit and to operation of said transmitting circuit for controlling the impedance of said electron discharge device.

In Witness whereof, I have hereunto set my hand this 13th day of January, 1927.

' LESTER F; BIRD. 

